I'm still not convinced by this, but I was chatting to Mix Master El Bastardos Rock Star about it yesterday and he made a couple of points:
"...the thing is that BT enables you to have a nice level of anonymity and be playful before committing yourself. I think this is what people like... also the immediacy of it (i.e. the fact that it's someone nearby) probably gives somewhat of a kick."
The idea of "playfulness" and its important in this sort of communication isn't something that had occurred to me. Mind you, then he said:
"I do think it would be quite nice though if your personality could be tattooed on your forehead as a bar code (as you once aspired to). I think we should then be given optical scanners and scan each other to see if we are interesting. That would be cool."